Three major studies are described. (1) Effects of androgenic stimulation of female dogs at different periods in development on hormonal and behavior cycles in maturity. Different groups are exposed to testosterone before birth, immediately postpartum, or both; and beginning at 4 months all subjects are monitored periodically for signs of ovarian cycles. Tests include, (a) plasma levels of estradiol and progesterone, (b) attractiveness of the bitch and of her urine for stud males, (c) tendency of the bitch to approach and sexually-solicit males, and (d) readiness to stand for the male and permit attempted copulation. (2) Development and maintenance of social organization in groups of dogs from birth to adulthood. (a) Within-litter tests are conducted from birth to determine relative social rank of each individual in terms of competition for teat position and for possession of a small bone. (b) Between-litter tests begin at 30 days. In both condition "a" and condition "b" tests of the group as a whole alternate with dyadic tests in which each member is tested against every other member. (c) At 60 days postpartum groups of subadults are introduced permanently into already-organized groups of mature males and females to permit observation of ways in which younger dogs become integrated into "adult society" and how they establish and maintain dominance status in the mixed goup. (3) Effects of prenatal and postnatal androgenic stimulation on development of urinary behavior in male and female dogs. Periodic observation from birth to 2 years in made of urinary behavoir of normal males, castrate males, males treated with TP from birth, normal females, and females treated with androgen at different stages of development from embryonic life to 90 days postpartum.